Downdraft hob or overhead extractor in recirculating mode

[SteamyTea]

9 minutes ago, G and J said:

do I serve it on rice

As you are from Suffolk, probably potatoes.

With some Saffron for colour.

Edited August 11 by SteamyTea

[G and J]

17 minutes ago, SteamyTea said:

With some Saffron for colour.

I’m more of a turmeric kinda guy…. 

[Pocster]

As a (expletive deleted)ing expert chef I can tell you a down extractor is awesome ( recirculating ).

No moist air and no smells ( washable carbon filters ) . On my elisia to get ‘full’ extraction you do need power 8 out of 10 . But with standard cooking 5/6 is fine . Just as noisy as an overhead tbh .

Been using it for over 2 yrs . My mates Ramsey and Oliver came over and they loved it - they are both twats though .

Edited August 11 by Pocster

[SteamyTea]

13 minutes ago, Pocster said:

Ramsey and Oliver

Could be worse, Antony Worrall Thompson and Ainsley Harriot.

 

May all your doughnuts look like Fanny's.

 

Keith Floyd and Graham Kerr for me, and Graham is still alive, missing half his fingers mind.

 

 

 

You have unusual vegetables.

[Tom]

I've got a recirculating downdraft going in soon and have often mulled the idea of plumbing an ozone generator in to the exhaust outlet to help with smells - reading the above it seems this is probably unnecessary. Just wonder if it might be worth a go though, or if it's even possible. Any thoughts?

[Russdl]

Based on our experience that would be unnecessary. 
 

You could always retrofit later if you felt the need but I’d be surprised if you did. 

[Adrian Walker]

2 hours ago, Tom said:

I've got a recirculating downdraft going in soon and have often mulled the idea of plumbing an ozone generator in to the exhaust outlet to help with smells - reading the above it seems this is probably unnecessary. Just wonder if it might be worth a go though, or if it's even possible. Any thoughts?

Not necessary and ozone is not good for you. 

[Post and beam]

Thinking a little more about this whole recirculate or extract thing. I get that opinion is divided about the airtightness hit bit. But, in a highly airtight building, if large amounts of air are being extracted it will have to be replaced from somewhere. The MVHR will be calibrated to a balanced configuration.

[Russdl]

That’s a good point @Post and beam I wonder what the MVHR does when the extract air + cooking extraction  is in excess of the supply air. It can’t know that you’re extracting more than it’s supplying can it?

[Adrian Walker]

27 minutes ago, Russdl said:

That’s a good point @Post and beam I wonder what the MVHR does when the extract air + cooking extraction  is in excess of the supply air. It can’t know that you’re extracting more than it’s supplying can it?

You don’t need to extract cooking in an air tight and well designed MVHR system. 

[Nick Laslett]

Remember that you can open windows any time with an MVHR system. This just affects its efficiency. The main concern with an external venting cooker extract, is that it creates a permanent air leak in the system. I do not believe there is a significant air pressure balance issue with this, but, I could be mistaken in this point. Passive House & MVHR does not preclude an external cooker extract, it just needs to be factored into the system design. There are Passive House certified extract ducts with air tight seals. When I was researching MVHRs back in 2019, there was good evidence that an MVHR system was beneficial and cost positive even in a house with an air tightness above 1.0 ACH. The goal would still be to have very good air tightness and try to reach the PH 0.6 ACH figure. 
 

https://passiv.de/downloads/05_extractor_hoods_guideline.pdf

Edited August 13 by Nick Laslett

[Russdl]

29 minutes ago, Adrian Walker said:

You don’t need to extract cooking in an air tight and well designed MVHR system. 

Agreed, but it seems that is the preference of some.
 

I just wondered what effect it would have on the MVHR if you’re extracting more air than it’s supplying for a protracted period, sure no house is completely airtight so the leaks will balance any under pressure created which I suspect would be insignificant. 

[dpmiller]

Intake fan will just freewheel a bit as the air is pulled through it...

[SteamyTea]

7 hours ago, Russdl said:

just wondered what effect it would have on the MVHR if you’re extracting more air than it’s supplying for a protracted period

 

1 hour ago, dpmiller said:

Intake fan will just freewheel a bit as the air is pulled through

Basically yes.

 

More air will enter via the MVHR and less air will exit via it.

Overall the MVHR will allow the same amount of air though it, just in an unbalanced manner while the kitchen extractor is on.

You could not put any MVHR pipework into the kitchen and have a basic through the wall heat recovery unit, and the hob extractor, or if you fancy a bit of DIY, fit some electrical isolator valves in the ductwork to isolate the kitchen when the hob is on.

 

Or just don't over think it and sleep peacefully.